Braun tube, more particularly for television purposes



D 24,-1940- K. ISCHLEDSINGER 2,226,107

BRAUN TUBE, MORE PARTICULARLY FOR TELEVISION PURPOSES .70 ban For:

Dec. 24, 1940; V K. SCHLESINGER 2,225,107.

I BRAUN TUBE, MORE PARTICULARLY FOR TELEVISION PURPOSES Filed Dec. 5, 1954 2 Sheets-Sheet'2 0/? ven for:

Patented Dec. 24, 1940 UNITED STATES poration of New York ApplicationDecember 5, 1934, Serial N o. 7 56,126

- 1, In Germany December 9, 1933 scams. 250-152) In Patent No. 2,126,286 to K. Schlesinger there is'described a Braun tube'for television purposes, in'which electron-optical systems are employed,

which-consist of suitable combinations of electrostatic electron-optical collecting and dispersing lenses. v

The present invention relates to ffurther developments of Braun tubesvcomprising electron optical systems. I I

The invention relates to a particular embodiment of the electron-optical systemsand" to Braun tubes furnished with systems of thischaracter.

Accordin'g'to the invention, 'there are employed for producing'the electrostatic'fields acting as ,c'olleoting and/or dispersing lenses cylindrical elements which are raised to different potentials.

In accordance with the invention; the refractive power of the electron-optical lenses may be adjusted as desired byvarying the biases and 120 the spacial relation of the two cylinders and by selection of the cylinder diameter. 7 I

If it is desired that the refractive 'power of the one electron-optical lens should be less than that of the other, the diameter of the, cylinder corre- 125 sponding with this lens is, in accordance with the invention, considerably increased, so that in the samea practically fieldlessspace results. Instead of reducing the diameter of theother'cylinder it is also possible to. close the, particular cylina 3 der by means of a diaphragm having an' aperture,

the diameter of which is smaller than the diameter of the cylinder. I

Ifas for example in the case 'of amplifier tubes according to the transverse field prinf ciple' -concentration of the bundle'of electrons is necessary only in one direction, the cylinders, in -accordance with the invention, may be replaced in equivalent fashion by pairs of condenser plates or preferably by metallic boxes. I

40 The present invention may be best understood by referring to the drawings wherein- Figures 1, through 5 illustrate the efiect of electrostatic fields to produce an electron lens, and

I Figures 6 through show the incorporation of electron lenses in the path of an electron beam. land 2 are in each casethetwo cylinders, and 3 closure 'diaphragms; By the number of connected with a weaker positive potential than -PATE Tf'JOFFIZoEf,

BRAUN TUBE, MORE PARTICULARLY FOR 1 TELEVISION PURPOSES Kurt Schlesinger, Berlin, Germany, assigiior, by

mesne ass1gnments, to Loewe Radio, Inc., a corv .versalof thetwo refractive effects may be accomplished simply by reversing th'ebiases H 7 crease in the.diameter.of that. particular tubular 10 effective space is to be produced, as shown in refractive efiect, i. e., for increasing the focaldissigns there indicated-the stateof. charge of lens with simultaneous acceleration. I

the cylinder 2, acts as combinationtoi aicollecting lens with a dispersing lens. of equal power. Re-

In numerous cases it is desirable to make one- '5 of the. tworefractive iforc'es smaller than the other. g I Y According to the invention, this may be:ac-. complished .for example-by a. considerable .,m-

system in whichapractioally fieldless, i. e., in-' Fig. lav InFig. 1a the..diameter of the inlet tube I is considerably smaller than the: diameter of the outlet tube 2. In this mannerit ifsaccomplished that the focal distanceofthecollecting lens is shorter than-the focal distance offthe dispersing lens. r i. p I Additional arrangements according to the invention for obtaining a predominantly one-sided tance of one of the two lenses,'are illustrated by way of example in Fig-s.2-5. f

In these lenses the reduction in cross-section takes place by means of a diaphragm-like ele- '25, ment 3, which is linked upwith' the same potential as I or Zdependent on the fact astowhether the focal distance ofthej collecting lens or that of the dispersing lens is to be reduced. A v

As apparent from the record of the appertainf- 30. ing potential line and field line diagrams, the ray in the case of thesearrangements is acted upon primarily only in the space between the diaphragm 3. and the tubular portion'notconnected therewith, whilst owing to the 'smallfield reciprocal in the space of same potential en'- closed by the diaphragm- 3 Variations in the direction of the ray in this lattermay be ignored.

This applies all the more the smaller thejdiameter of the diaphragm aperture inrelationto the "40 diameter of the tube and the greater'the distance betweenthe ends of the tube. The diameter of the diaphragm aperture determines the greatest effective aperture.of'the lens'.1 v

The arrangement according to Fig. 2, "iff the ray passes from theleftto the right and! is ,cbnnected with alowerpotential than 2, acts in the manner of a collecting lens within .I ithsi'multaneous acceleration." I

The arrangement according to Fig. 3 Wlthsifn-filar supply of the potential, acts as a dispersing The arrangement according to Fig fl, withsupply of the potential'as stated, acts as dispersing.

lens with retardation within I, whilst the arrangement illustrated in Fig. 5 acts as collecting lens with simultaneous retardation within 2.

As an example of the use of the lenses according to the invention there are described in the following two constructions of television tubes.

In tubes of this nature there exists the problem of reproducing sharply the aperture of a diaphragm 4 in an image-screen plane 5 as far as possible on reduced scale. The most simple arrangement for solving this problem consists of a .collecting lens disposed as closely as possible to the screen 5 and as far away as possible from the diaphragm aperture 4. Since it is necessary to impart to the electrons when reaching the screen the highest potential capable of being supplied by the potential source (in order to obtain maximum intensity of light), there is suitable for this purpose a collecting lens, which acts as accelerating lens, 1. e., which simultaneously imparts to the ray an acceleration.

A lens'of this nature is illustrated in Fig. 6. The same consists of a tubular member I, which is as wide as possible and accordingly permits of the use of thick bundles, in front of a diaphragm 8 which somewhat reduces the cross-section, I having a lower potential than the diaphragm 8 If the diaphragm 8 with its reduction of crosssection is omitted, there is formed, subject to at least partial conductivity (for example provision of a metallic coating) and charging of the wall of the bulb 9 to the high potential a combined lens system corresponding with Fig. 1, in which following on a collecting lens, which is to be considered as being arranged in the tube 1, there is a dispersing lens, which is to be regarded as being localised in the bulb portion 9. Assuming that the diameter of the part 9 is larger than the diameter of the tube 1, an arrangement of this nature also acts primarily as collecting lens according to Fig. 1a; the same, however, possesses the disadvantageof decrease of the refractive power with large displacement of the bundle of rays out of the axis.

By combination of a dispersing lens with a collecting lens, which may be arranged at a relatively large distance apart, it is possible according to theinvention with the same length of tube to obtain a better reduction of the image point than occurs in the case of the single-lens tube described in Fig. 6 (reversed tele-objective) In Figs. 7 and 8 there are shown two forms of embodiment of Braun tubes according to the invention, making use of the accelerating or retarding lenses described in Figs. 1-5.

As shown in Fig. 7, there is employed a diaphragm 4, which is lighted for example by means of the condenser arrangement described in the following and is preferably connected with a comparatively low positive potential (for example 100 volts).

The total length of the tubular portion up to the point 6 (i. e., up to the collecting lens) may be the same as in the case of the single-lens tube according to Fig. 6. At this point 6 there is provided in accordance with the invention a final anode raised to the highest potential occurring and having an aperture exceeding the largest cross-section of bundle. A tubular portion ll! of approximately half the total length of tube $4; available is linked up with the potential of the diaphragm 4 Between I and 6 there is provided an additional tubular portion ll,

which joinsup with the tubular portion I 0 and to which there is imparted a medium potential There is then formed between I0 and H in the manner indicated in broken lines a dispersing lens with simultaneous acceleration according to the diagram of Fig. 3, and between the tubular portion II and the main anode 6 a collecting lens with additional acceleration according to the diagram in Fig.2.

To explain the passage of the rays obtained by the arrangement there is shown in the drawings an arrow l2 in substitution for the object (diaphragm aperture 4). Of this there is produced in the maimer stated by the dispersing lens l3 a reduced virtual image l4 on the side directed towards the object, i. e., within the tubular portion Iii. By suitable selection of the focal distance of the collecting lens l5 there is projected in the plane 5 of the luminous screen a reversed, correct reproduction I6 from the image l4. This image is considerably smaller than the images capable of being obtained with the same length of tubular member when employing solely a collecting lens (image H). The adjustment of the focal distances, with given geometric dimensions, may be performed in simple fashion according to the invention by adjustment of the relative differences in potential between the mutually insulated electrodes forming the particular lens on the one hand and on the other hand).

A tube having the same electronic optic but with different accelerating and retarding conditions is illustrated in Fig. 8. In this arrangement also a diaphragm aperture 4 is lighted with a bundle of electrons as parallel as possible. Connected with 4 is a tubular portion I0 raised to medium potential Opposite the opening of the tubular portion ill there is situated a diaphragm l8, which is insulated against the same, and with which the tube H is connected and raised to the lower potential In front of the latter tube there is provided an anode 6 raised to the maximum potential available There is again obtained a dispersing lens in the indicated position l9, which acts as retarding lens on the lines of Fig. 4, and a collecting lens 20 with simultaneous acceleration on the lines of Fig. 2.

A further object of the invention are means for lighting the small diaphragm aperture 4 representing the object to be reproduced with the greatest possible density of light and smallest possible opening of the bundle of rays. The latter requirement is particularly important in tubes according to Figs. '7 and 8, which operate with combined lens systems, as in tubes of this nature a bundle which already diverges in the diaphragm aperture 4 may assume such an expanse that at the point of the final concentration lens (I5 or 20 in Figs. 7 and 8 respectively) it is not fully embraced by the lens aperture and, therefore, is weakened in part by selection. Since the bundle leaving the lens takes up merely a small angle in space about the axis face of which is determined ,by" the; desired maximum emission (spot' of 'oxide ofathei order' of approximately .'5-1smm. This: spot. of; oxide for the purpose of producing defined potential areas; in such into a piece of metal 22;;thesi'1rface of which .islarger than that; ofltlrei oxide :andlis, foriexample, ground flat At a distance' 23; front of. this cathode? which: is freely 'sea :lectiva initself there: is provided the diaphragm A 1 having a. very small: aperture: (for example I also .5. mm.)i, .which is raisedtoa-positive -poten+ tial as prescribed bythe-remaining elec .tro-noptical system 1 and the maximum existing anode potential.-- It isnecessarythat as-iarge a fraction as possible (in theideal case}100%) of the: flow of electrons from the cathode 2=l should passtthrough thesmall apertnre of 4.; Hereto fore. it has been attempted to-solve this problem by projecting within the diaphragm aperture of 4 atrue reproduction of equal or reduced sizeof the cathode surface 2 I by means-of a-col lecting. lens -(24-)- disposed,between the same and these' rays stake up an excessively large angle of the diaphragm 4.. -The disadvantage of this method consists fundamentally inthefact that although it is possible topassall raysthrough 4 divergence and accordingly are lost in part in the.- rear sections-of the extended optic-by selecray and tubular length of'ray with given size .tion' outside of the reproducingdenses provided at that point... 1

1 In; the above-referred to-Patent No; 2-,l-26, 286

apertures delighted.withoutdoss, may be made :with algiven cathodesurface 2t, the shorter-are the televisionv tubes, andthe more parallel the bundle ofv rays ismade theggreater imay be the dispersionsv employed in the method according to Figs. 7. and 8 without the-bundle afterwards possessing aninadmissibly great cross-sections These features all assist towards a reduction in the structural lengthuof the tube. and in an improvementin the sensitiveness of deflection .by increase of the ratio between deflectedlength of ofima'ge field and image point, e

1 According to the invention, there are alsoplayed for lighting'the diaphragm arrangements oiithe lines of the systems described at the come m'ericement. This may takeplace, fore'xampl'e,

in the'following'm'anner:

At as short'a distance aspo'ssible from the ca'tho de surface 2 2% there is provided a s'uctional anode :26 having a comparatively large aperture; for-example 2e3 min; According to the' invention;

the combination of. the two lenses 24) 25 ispro: du ed-by a-double-cylinder arrangement without intermediate diaphragins on the lines of-thean rangement illustrated in Fig-. 1, in such fashion cylinder 28 -01; theQsame diameter; These c37 inders are distinctly determined both asregards their; lengthl a's well as their diameter *by'the,

potential' prevaili'iig at: the diaphragm 4' and by theysize' of this diaphragm/and of thespot of oxide. 1f it isdesire'd that in' addition 30 bhe c on' ram;

centration effect always presents in the front lar'me'mber 28i sholildzat leastfbe iqual toand ,preferablygreatier to the xextent'iof app'roxi mately'twice the amount*thanz the length of .thefronttubul'ar member: 21, as may be proved by making a recordv ofthepotential line dia+ On'the otherihand' it hasbeen found con venient according tozthe invention'to connect the front tubular member-'21 electrically. with the suctional anode 26, and also" the rear tubular member 28 with the diaphragm 4, asjin this manner the formation of additional lens-fields at the transition pointsbetw'een the stated electrodes is avoided. Assuming the bias Ofnthfi dia phragml to be approximately 300v'olts ,(+-l-'), as'will be the case, forexample, in atube according to Fig. 6 with altogether 2000 volts anode potential and a scale of "reproduction of 1:1, the potential of the-suctional anode 26 as well as that of the'front-itubular' member 21' must be lower than 300,vol t's;(-|-,) l

It is desirableaccording to the invention not to make the potential at.2'| :too low in order to prevent reduction of'theiemission.

The passageof the rayin-thec'ondenser is determined by. the ratio between the radial field intensity and the-particular speed of the electrons.

, According tofthe invention, the former is increased by reducing in proportion the entire di ameter and longitudinal dimensions of the condenser. With b-iasses maintained constant all field intensities inthe interior of the condensers are thus increased in proportion. In this manner it is possible to reduce the requisite differ-- ence in potential between the suctional anode 26 and the diva phragmfl, and to increase the difference in potential between the suctional anode and zero). ,H r

The arrangement may be dimensioned, for example, as follows:

Cylinder diameter-of 21 and 28: 10mm. In

this connection 2'! was 10mm. in length and 28 was 20 mm. in length; Cathode 2|: .3 mm. diameter. Diaphragm; aperture: .5 mm. diameter. Length of tube: 500mm. In this connecr tion the potential at 4-was300 volts Potential at 26: 30 volts. By reducing the diameter and length of the cylinders to one-half or onethird the potential at 26 may be raised toapproximately twice to three times the amount,

and in this way'the maximum emission .of the arrangement increased accordingly.

, A' condenser arrangement of this character, as illustrated by way of example in Fig. 9, may be thecathode (with the potential controlled in faultless manner as regards its intensity by means ofv a diaphragm-like control grid29 through. the medium of a control potengrid 29 may inf practice also possess a greater diameter thanthe cathode (1-2 mm. )y:and is preferably approached as near towards the spot of oxide as possible in order to increase the V steepness of the control. According to theine vention, the same may; be arranged at a distance of approximately 1 mm. or even less from the cathode 2-l and suctional anode-26, -The appucant "has already'set forth on a previous oc'ca'sion the manner in which an arrangement of this nature may be centred mechanically The cyl inders 21' and 23. are conveniently: engaged by set on collars'l land 26, and the lattercentred in relation to each other-by means of common glass rods 31 passing through borings in these collars. Inplace ofthe. rods there may also be employed glass. tubes, and in the borings thereof the leads to other parts of the system arranged in insulated fashion. These. measures are of particular importanceas regards the arrangement according to the invention, as it is a matter of axially centring a condenser system-of this nature which isprecisely concerned owing to the appreciable increase angularly in the lack of symmetry later taking place. H

It. will be quite obvious that. the sizes and potentials are quoted merely byway of example, and require to be varied accordingly when changing the measurements of the tube or the operating potentials. i I

Both the condenser opticas well as reproducing optic according to the invention may be employed quite readilyin Braun tubes of a desired kind, and more particularly high-vacuum tubes for television purposes, and also other discharge vessels, for example amplifier tubes according to the transverse field principle.

It is also quite readily possible to modify the stated forms of embodiment in the r details without departing from the fundamental idea of the invention.

There shall be remarked that it may be possible in some cases to replace a cylinder having an apertured diaphragm by an apertured plate of corresponding dimensions.

In the preferred embodiment of the invention a Braun tube may contain the combination of a first electron-optical system for example as shown in Fig. 9 with reproducing ystem, for example, as shown in Figs. 6-8,'as illustrated by way of example in Fig. 10 which shows, Within an envelope, an electrode structure according to the invention in an entirely diagrammatic fashion, means being provided for supplying the different electrodes with the necessary potentials. Such means may consist in a manner known per se of one or more potential sources. If one potential source, for example, a battery, be used, the same may be bridged by a potentiometer having several tappings which correspond to the different required voltages. Different elements having to be supplied with the same bias may be connected inside the tube with one another. The Braun tube further comprises a picture receiving screen and deflecting means such as two pairs of deflecting plates for the purpose of scanning said screen. The deflecting means may be such that they are not able to'produce a disturbance of the electric concentrating field. In the case that electro-static deflecting systems be used, to the one plate of each-deflecting system the deflecting voltage and to theother plate a voltage should be applied, whichis equal to said defleeting voltage asto its potential, but which is of reverse phase. With the-use of such systems disturbances of the concentrating field easily may be avoided.

The electron-optical systems of the invention follow approximately the formula spanner of: this formula, though- -the focal distance beinga'djustable at Will.these distances determine the size. of the image point. only.

'I claim:;

1. Ina cathode ray tube comprising means for; producing a cathode beam, a diaphragm having an aperture disposed in the path of the cathode beam, a beam receiving target and means for producing in the space between said diaphragm and said target an electron-optical lens field for producing on said target an electron image of the aperture in said diaphragm, means for preconcentrating the electron beam onto the aperture in said diaphragm comprising two coaxial cylindrical elements of substantially equal diameter displaced axially on the side of said diaphragm remote from said target, the whole cross-section of said cylindrical elements being open at their ends facing each other, said two cylindrical elements positioned coaxially with respect to the aperture in said diaphragm, said two cylindrical elements being adapted to have difierent potentials impressed thereon to produce tne combination 01' a converging and a diverging electron lens.

2. In a cathode ray tube comprising means including an electron source for producing a cathode beam, a diaphragm having an aperture disposed in the path of the cathode beam, a cathode ray intensity control electrode, said cathode ray intensity control electrode being mounted in the vicinity of said source between said source and said diaphragm, a beam receiving target and means for producing in the space between said diaphragm and said target an electron-optical lens field for producing on said target an electron image of the aperture in said diaphragm, means for preconcentrating the electron beam onto the aperture in said diaphragm comprising two co-axial cylindrical elements of substantially equal diameter displaced axially between said control electrode and said diaphragm and positioned substantially coaxially with respect to the aperture in said diaphragm, the whole cross-section of said cylindrical elements being open at their opposed ends, said two cylindrical elements being adapted to have different substantially fixed potentials impressed thereon to produce the combination of a converging and a diverging electron lens.

3. In a cathode ray tube comprising means including an electron source for producing a cathode beam, a diaphragm having an aperture disposed in the path of the cathode beam, a cathode ray intensity control electrode, said cathode ray intensity control electrode being mounted in the vicinity of said source between said source and said diaphragm, a beam receiving target and means for producing in the space between said diaphragm and said beam receiving target an electron optical lens field for producing on said target an electron image of the aperture in said diaphragm, means for preconcentrating the electron beam onto the aperture in said diaphragm comprising two coaxial cylindrical elements of substantially equal diameter displaced axially between said control electrode and said diaphragm and positioned coaxially with respect to the aperture in said diaphragm, the whole cross-section of said cylindrical elements being open at their ends facing each other, said two cylindrical elements being different in length and adapted to have different substantially constant potentials impressed thereon to produce the combination of a converging and a diverging electron lens.

, 4. A cathode ray tube comprising means ineluding an electron source for producing a cathode beam, a diaphragm having an aperture disposed inthev path of the cathode beam, means for preconcentratingthe electron beam onto the aperture in said diaphragm comprising two i in axial cylindrical elements of substantially equal 7 diameter displaced axially between said source and said diaphragm, said two cylindrical elements having the aperture in said diaphragm centrally aligned therewith, said two cylindrical elements being adapted to have *diiTerent potentials impressed thereon to produce the combination of a convergent and a divergent electron lens, a beam receiving target at the end of the cathode 1 ray tube remote from said source, and an electron-optical system mounted between said diaphragm and said target for electronoptically reproducing the aperture in said diaphragm on said target, said electron-optical system comprising two axially displaced tubular members positioned coaxially with respect to said cylindrical elements and betweeen said diaphragm and said beam receiving target, and an apertured. plate mounted adjacent the end of each of said tubular members facing said beam receiving target..

5. A cathode ray tube comprising means including an electron source for producing a cathode beam, a diaphragm having an aperture disposed in the path of the cathode beam, means for preconcentrating the electron beam ontothe aperture in said diaphragm comprising two axially displaced coaxial cylindrical elements of substantially equal diameter mounted between said source and said diaphragm, said two cylindrical elements being positioned coaxially with respect to the aperture in said diaphragm, said two cy-' lindrical elements being adapted to have different potentials impressed thereon to produce the combination of a convergent and a divergent electron lens, a beam receiving target at the end of 'the cathode ray tube remote from said source,

and an electron-optical system mounted between said diaphragm and said target for electronoptically reproducing the aperture in said diaphragm .on said beam receiving target, said electron-optical system comprising two axially displaced tubular members mounted coaxially with respect to said cylindrical elements and positioned between said diaphragm and said beam receiving target, andian apertured plate mounted adjacent the end, facing said beam receiving target, of each of said tubular members in a crossa "space between said diaphragm and said target an electron-optical lens fieldfor producing on said target anelectron image of thejaperture in said diaphragm, means for preconcentrating the electron beam onto the aperture in said diaphragm comprising two coaxial cylindrical elements displaced axially between saidcontrol electrode and said diaphragmand positioned substantially coaxiallywith respect to the aperture in said diaphragm, the i whole cross-section of said cylindrical elements being open attheir opposed ends, said two cylindrical elements being adapted to have difierent constant potentials impressed thereonto produce the combination of a converging and diverging electron lens.

KURT SCHLESD TGER. 

